There is some irony in that Aslef's withdrawal of rest day working is increasing the problem they say they are trying to avoid - messrooms which used to be quiet are now chock-a-block with drivers and guards sitting around because the trains they should be working on are cancelled.
I'm still not sure we are all fully understanding exactly what spare drivers are for and how they are utilised.
If an operator has taken the step to cut back the service as a consequence of staffing issues, you can be sure that as many drivers as possible have been allocated work. Therefore you won't have messrooms chock-a-block with traincrew sitting around. If the messrooms really are as busy as you suggest then you have to wonder why is it the TOC isn't running more services.
And the same point also suggests Aslef is wrong too.
They are assuming that by returning to normal working and getting rid of spare at home then suddenly mess rooms will be full of drivers sat around spare spreading covid to each other.
This would almost certainly not be the case - pre-covid the amount of spare people sitting around who hadn't actually been allocated work was so small it wasn't worth worrying about. It is even less likely now, so I simply don't believe there would be any pressure on mess room capacity at all.
I'm not sure that is what ASLEF are saying. My own reading of what has been coming down the chain where I work is that these are infection control measures by controlling the numbers of staff gathering and mixing in the workplace.
But yes, at this particular moment in time when spare staff are a rarity (well, except at Norwich it would seem

) the risks are currently low.
I don't know the situation at TPE, but it's worth remembering that not all TOCs have service recovery/standby/cover turns - some just have spare, which are used for everything whether they're planned in advance or covering a shift on the day. In these cases the spare crews *are* the service recovery.
We never had standby turns until the pandemic started. They were only instated as a consequence of spares being at home.
What, if not staffing, do you think is the cause of TPE's travails?
I would invite you to review the thread as you will find the information you seek already contained.